In the formation of glassware, it has been common practice to form a parison, in a parison molding portion of the glassware molding machine, to automatically transfer the parison to a blow molding portion of the glassware molding machine, and then to blow mold the parison into conformity to a blow mold.
Commonly, the parison blank mold has been formed in two mold halves that each include a mating surface. The mold halves open and close around a parison axis; and when the mold halves are closed, the mating surfaces are juxtaposed together, a blank molding cavity is formed that is disposed circumferentially around the mold axis, and the blank molding cavity includes a parison molding surface.
A neck ring, that includes a pair of neck ring halves, is juxtaposed against the bottom of the parison blank mold and is clamped between grooves in the mold halves, a finish guide plate is retained in a groove in the neck ring halves, a parison baffle mold is provided to close a top opening of the inverted parison blank mold, and a parison plunger is movable upward into the molding cavity.
The blow mold portion of the glassware molding machine includes a body mold having a body molding cavity. The body mold includes both a body side mold and body bottom mold; and the body side mold includes body side mold halves that open and that close around a blow molding axis.
In operation, a gob of molten glass is deposited into the parison molding cavity, the parison baffle mold is placed over the top of the parison blank mold to close the top opening of the parison molding cavity, and the parison plunger moves upward within the parison molding cavity to form a parison within the parison blank molding cavity and the parison finish molding cavity.
The baffle mold is removed, the mold halves are opened, the parison is supported by the finish mold, and the finish mold, together with the parison, is transferred to the container body mold.
The body side mold halves close about the parison, the neck ring halves open to release the parison, the transfer device returns the finish mold to the blank mold, a blowhead is placed over the cavity opening in the top of the body mold, and the container body is formed to final size and shape. The blowhead is removed from the body mold, the body mold halves open, a takeout jaw moves to the body mold and closes around the finish, and the takeout jaw transports the container from the body bottom mold to a position for take away.
In the molding process described, it has been found necessary to lubricate the molding surfaces at frequent intervals during the production run, to prevent malfunctions of the process and to prevent both mechanical and thermal damage to parison and containers.
Commonly, lubrication of the molding surfaces has been a hand swabbing operation that is carried out periodically.
There have been at least eight types of problems, or limitations in the process, that have attended hand swabbing.
One problem has been that there is insufficient time to carefully swab the molding cavity during automatic cycling of the glassware molding machine. A second problem has been that hand swabbing has not deposited a uniform layer of lubricant onto the molding surface. Therefore, sufficiency of lubrication and the required frequency of hand swabbings have been two of the larger variables in the glassware molding process.
A third problem is that times between swabbings have been erratic due to other duties of the machine operator. A fourth problem is that there has been a tendency for machine operators to apply an unduly heavy coating of lubricant in an attempt to adequately swab the entire molding surface and/or in an attempt to swab less frequently.
A fifth problem has been generation of excess smoke in the work area due to the operating temperatures burning excessively heavy deposits of hand-swabbed lubricant off of the molding surfaces. A sixth problem has been contamination of parisons by excessive lubricant and a resultant reduction in the strength of the finished glassware.
A seventh problem has been that the mold halves have been open during hand swabbing. This has resulted in an accumulation of lubricant residue on the mating surfaces of the mold, incomplete closing of the mold halves, development of a fin of glass from the parisons that extend outward between the mold halves, and a resultant reduction in the strength of the finished glassware that is blown from parisons having this kind of surface irregularity.
An eighth problem with hand swabbing is that it is impossible to accurately lubricate selected portions of the molding surface more heavily than other portions. This precludes adequately lubricating surfaces that require greater lubrication without producing defects due to over lubrication and/or generation of excessive smoke from burning excessive lubricant.
There have been various attempts to lubricate the molding surfaces automatically.
Bjorkstrom, U.S. Pat. No. 3,981,711, teaches an automatic swabbing operation in which a swab is alternately dipped into a container of lubricant, and is alternately moved downwardly through both the parison blank mold and the neck ring. Bjorkstrom does the swabbing operation while the mold halves are closed; and he provides an air nozzle for distributing the lubricant and for blowing away excess lubricant. Of course, running a swab that is dripping with lubricant into the mold cannot provide a controlled application of lubricant, nor can it selectively coat selected areas with more lubricant than other areas.
Keller, U.S. Pat. Nos. 3,141,752, 3,623,856, and 3,721,542; Mumford, U.S. Pat. No. 3,814,594., Hubner et al., U.S. Pat. No. 4,578,099; and Brown, U.S. Pat. No. 4,604,120., all show mechanisms in which lubricant is sprayed into the parison molding surface from a position above and outside the parison blank mold. This position of the spray jet precludes uniform coating of either the parison blank molding surface or the parison finish molding surface.
The above-referenced patents which disclose spraying lubricant into the parison blank mold disclose various devices for moving the spray head out of the way during the molding process.
In addition to teaching lubrication by spraying a mist of lubricant downward into the parison blank mold, Hubner et al. teach the use of jet of air from the parison plunger head for preventing the mist of lubricant from settling onto the parison plunger and thereby causing defects in the parisons. While this method is feasible where only the parison blank mold is to be lubricated in the absence of the parison finish mold, it would not be feasible where both the blank and finish molds are lubricated while closed together as in the present invention.
Brown, U.S. Pat. No. 4,409,010, teaches spraying the lubricating mist onto the blank mold halves while they are open. The obvious problem with this is that the mating surfaces of the mold halves are coated with the lubricant, resulting in a build-up on the mating surfaces, defects in the parisons, weakened glassware, and downtime for cleaning off the deposits.
Sugie et al., U.S. Pat. No. 4,579,574, shows apparatus in which lubricant is sprayed upward, and at an angle to the mold axis, into the neck rings and into the blank molding cavity. Of course, it is impossible to accurately and uniformly coat the parison molding surfaces with jets that are located outside of the parison molds and at an angle to the mold axis. In like manner, it is impossible to coat selected areas with a greater quantity of lubricant than other areas.